What are the feature of metal flow during forward extrusion?
Cold extrusion process principle: under normal temperature, according to the principle of plastic deformation, using the mold installed on the pressure machine, the aluminum blank is put into the die through the punch, so that the blank produces plastic deformation at a certain speed and the parts with required shape, size. Aluminum extrusion is a processing method in which the aluminum ingot is loaded into the extrusion barrel, and the aluminum material is pressed through the extrusion shaft, so that it can be extruded from the die hole of a given shape and size, and the required extrusion product can be obtained through plastic deformation.
The metal flows in different directions during extrusion. Extrusion can be divided into forward extrusion, reverse extrusion and combined extrusion.
In the forward extrusion: the movement direction of the extrusion axis is consistent with the flow direction of the extruded metal.
In the reverse extrusion: the movement direction of the extrusion axis is opposite to the flow direction of the extruded metal.
According to the heating temperature of billet, extrusion can be divided into hot extrusion and cold extrusion. In hot extrusion, the billet is heated above the recrystallization temperature for extrusion, while in cold extrusion, it is extruded at room temperature.
In aluminum extruder, cold extruding and hot extruding are essentially belong forging, not extrusion. Is there a some difference between them.
However, the difference between cold extrusion and hot extrusion can be understood as the difference between cold pressing and hot pressing. Hot extrusion generally heats the material to a certain temperature or softens it and then puts it into the mold to extrude the workpiece in need of shape, which can reduce the extrusion pressure but change the properties of the material. Cold extrusion generally does not heat the material, directly extrude, so it need a lot of extrusion pressure, but basically do not change the initial state of the material.